There are many medical procedures where a surgeon needs to attach soft tissue to bone. The soft tissue can be tendon or other connective tissue. One very common example of this is rotator cuff repair where a portion or all of the rotator cuff is torn or detached from the humerus. When the rotator cuff tears from the humerus, the result is pain and loss of function. Rotator cuff disease affects a large number of people worldwide, affecting many people over the age of forty. Some studies have shown a prevalence of approximately 30% in people over the age of forty (Rockwood C., et al., The Shoulder, Saunders, 2004; 820-821). It is estimated that as many as 17 million people in the United States may be at risk for pain and dysfunction as a result of rotator cuff injuries. While the majority of people are asymptomatic, a significant subset goes on to have disability. One study in patients with rotator cuff tears in one shoulder found that 50% of these patients who had an asymptomatic rotator cuff tear in the other shoulder went on to become symptomatic (Yamaguchi, K., et al., J. Shoulder Elbow Surg., 2001; 10:199-203).
The prevalence of symptomatic rotator cuff disease is reflected in the large numbers of surgical repair for this condition. Rotator cuff repair is one of the most common orthopedic procedures performed. When a patient presents with a significant rotator cuff tear, surgical repair is performed. The goal of surgical repair of the rotator cuff is to secure the tendon to the bone in a stabile manner so that the tendon and bone can heal. If the tendon is not stabile and oscillation or micro-motion between the tendon and bone develops, the healing process will be interrupted. In this situation, it is less likely that the tendon will heal properly to the bone, resulting in a re-tear. Thus, the more stable the repair, the more successfully the tendon will heal to the bone.
Rotator cuff repair is performed open or arthroscopically, most often using suture anchors. These have one point of fixation with either one suture or several sutures attached for attaching the tendon to the bone. While arthroscopic repair is less painful and thus more attractive to patients, many surgeons continue to perform open rotator cuff repairs. Much of the reason for this is due to the challenge of arthroscopic shoulder surgery. There is a significant learning curve in gaining the skills to be able to manage multiple strands of suture in a relatively small field of view, passing these through the tendon and tying them down. Many of theses techniques can be relatively time-consuming when compared with open surgery.
There is a growing body of literature showing that surgical rotator cuff repair has a high rate of failure. Failure of rotator cuff repairs is a well-described complication of rotator cuff repairs, both open and arthroscopic. For example, Gerber et al. found a re-tear rate of 20% following isolated repair of the supraspinatus Fuchs found a re-tear rate of 20% following isolated repair of the supraspinatus (Fuchs B, et al., Clinical and structural results of open repair of an isolated one-tendon tear of the rotator cuff, J Bone Joint Surg Am., 2006 Febuary; 88(2):309-16). Liem found a re-tear rate of 31.6% in arthroscopic supraspinatus and 36.8% in patients undergoing mini-open repair (Liem D., et. al., Arthroscopy, 2007 May; 23(5):514-21). Galatz found an even higher re-tear rate in larger tears (Galatz, L., et al., The outcome and repair integrity of completely arthroscopically repaired large and massive rotator cuff tears, J. Bone Joint Surg. Am., 2004; 86A:219-24). Tendon-to-bone reattachment in a rotator cuff repair procedure can fail by a number of means. In a review of failed rotator cuff surgeries evaluated at re-operation, Cummins cited as one of the weak links in the repair, the suture-tendon interface (Cumins, C.A., et al., Mode offailure for rotator cuff repair with suture anchors identified at revision surgery, J. Shoulder Elbow Surg., 2003 March-April; 12(2):128-33). To reduce the load on any one suture, (i.e., greater distribution of loads) suture anchors used in tendon repair have begun to add multiple sutures to each suture anchor. Burkhart illustrates that the load on each suture diminishes as the number of sutures holding the tendon in place increases (Burkhart, S. S., et al., A stepwise approach to arthroscopic rotator cuff repair based on biomechanical principles, Arthroscopy, 2000 January-Febuary; 16(1):82-90). Kim demonstrated less strain and greater tendon-bone stability in repairs made with multi row (4 fixation points) than with single row (2 fixation points). However, even in the repairs made with 4 fixation points, slippage (oscillation and micro-motion) between the tendon and bone was greater than 3.0 mm after just 200 cycles of physiological loading (Kim, D., et al., Biomechanical comparison of a single-row versus double row suture anchor technique for rotator cuff repair, Am. J. Sports Med., 2006; 34; 407).
With current suture anchor based fixation techniques, it is difficult to get more than four points of fixation, particularly in arthroscopic repair, for two reasons. First, the challenge and time required to manage multiple sutures can greatly lengthen procedure time and complexity. Second, suture anchors commonly use a 5.0 mm diameter anchor that is anchored into bone. The typical footprint size (area that the tendon connects to the bone) for the supraspinatus tendon is 25 mm long and 15 mm wide. Placement of more than a few 5.0 mm diameter anchors into this area may significantly compromise the strength of the bone as well as disrupt the very bone that the tendon needs to heal to.
The concept of distributing physiological loads over multiple fixation points in tissue repair has been previously described by Jacobs (U.S. Pat. No. 6,893,452). Jacobs describes approximating soft tissue with a planar structure that contains multiple fixation points integrated onto it. Use of such a system in attaching tendon to bone would cover a significant percentage of the bone that the tendon needs to heal to and therefore may not be a desirable method for repairing tendon to bone.
Thus what is needed is a tendon to bone fixation method and device that will enhance the stability of the tendon to bone interface which in turn will minimize gap formation and tendon/bone micro-motion and provide a greater opportunity for the tendon and bone to heal properly. The ideal method and device would not require the use of additional sutures, but possibly reduce the number of sutures required to adequately stabilize the tendon to the bone, thus simplifying the procedure.